The overall goal of this project is to characterize the normal developmental process of the mouse brain using magnetic resonance imaging (MRI). The advent of mammalian gene engineering techniques using mice has been spurring studies of mouse brain development in molecular levels. Morphological analysis due to gene alterations has been mostly performed by histology, which is suitable for microscopic, cellular level examination. However, global and macroscopic morphological analysis by histology is not always straightforward. MR-based three-dimensional imaging techniques that can rapidly and precisely examine macroscopic morphology are, thus, in great need. Similar to various staining techniques in histology, MRI can produce various contrasts depending on data acquisition techniques. However, conventional MR contrasts such as T1 and T2 have poor capabilities to delineate fetal brain internal compartments. In this application, special emphasis will be placed on diffusion tensor imaging (DTI). This emerging technique is sensitive to the existence and orientation of ordered structures and can provide high contrast to segment various structures in fetal brains. The investigators' hypothesis is, "DTI, combined with conventional MRI, can discretely identify various components of developing mouse brains and, thus, it can rapidly and precisely characterize normal brain development processes". In order to confirm this hypothesis, they set the following three aims: Aim 1: To optimize DTI-based data acquisition techniques for rapid and precise depiction of 3D morphological features of brain development Aim 2: To acquire a preliminary dataset of developing mouse brains. Aim 3: To perform preliminary characterization of brain development based on the MR contrasts. Techniques and the database established under this project will serve as preliminary phase for more comprehensive normative developing mouse brain database and for development of image analysis tools to parameterize the development and characterize developmental abnormalities in the future.